It’s Better to Operate with Eyes Open – Applications and Perspectives of Intraoperative Ultrasound (IOUS) in Gynecological Procedures

Introduction

Intraoperative ultrasound (IOUS) is a widely used procedure, and it is becoming increasingly important in gynecological surgery [1]. Previously, the scientific focus of sonography in gynecology was on preoperative diagnosis and targeted treatment planning. In recent years, due to the rapidly growing evidence of the potential that gynecological sonography holds for diagnostic imaging, dignity assessment, and spread diagnostics of malignant (e. g. ovarian cancer) and benign processes (e. g. endometriosis), OB/GYN ultrasound has become part of many guidelines, expert recommendations, standardized quality requirements, and training programs [2] [3] [4] [5] [6].

In addition, a highly specialized expertise has developed along different paths in the sonographic and surgical fields. Unfortunately, it is rare to find well-rounded experts who bring the highest level of expertise to both general sonography and modern gynecological sonography. The communication interface between pre-op diagnostics and the OR is therefore of critical importance for the overall success of the procedure. For this reason, the potential applications provided by IOUS, i. e. putting sonography in the surgeon’s hands in the OR, can be a valuable tool.

In addition to the pre-op sonographic access options already available (transabdominal, transvaginal, transrectal, transperineal), particularly noteworthy approaches that represent clear extensions of the diagnostic options include sonography at the open situs and using specialized rod transducers via laparoscopy ([Fig. 1]).

Fig. 1 Laparoscopic setup for intraoperative sonography. A – Laparoscopic setting for placement of endoscopic transducers; B – Disinfectable operating surface of the ultrasound device with sterile cover; C – Flexible rod transducer in situ; D – Drop-in transducers in situ.

The specific benefits of IOUS are related primarily to the following aspects:

• High degree of mobility with comparatively easy accessibility

• Targeted anatomical correlation of preoperative findings

• Simplified sonographic access (e. g. in painful situs, in laparoscopic use)

• Real-time imaging with advanced features such as Doppler sonography or elastography

• Increased precision by protecting non-diseased or preserved tissue

• Improved control of the response to pathological findings

• High quality of documentation

• Reduction of the rate of complications.

IOUS is therefore used both for benign diseases and to improve surgical efficiency in gynecologic oncology while minimizing the burden on the patient [7]. In this regard, it should also be mentioned that some authors refer to IOUS as “the surgeon’s stethoscope” [8].

The following text is intended to provide an overview of the current application areas for IOUS.

IOUS in benign gynecological diseases

Non-pregnancy-associated intracavitary diseases

IOUS enables improved orientation of the surgeon during hysteroscopic procedures, such as the removal of septa, myomas, or polyps, as well as during synechiolysis, and reduces the risk of a perforation. In addition, studies show that the combination of IOUS and hysteroscopy promotes the completeness of the resection of submucosal myomas [9] [10] [11] [12] [13].

Early pregnancy

In the surgical treatment of disturbed early pregnancy, abortions, and hydatidiform moles, IOUS is used to reduce the rate of complications. Performing gynecological surgery procedures, such as dilatation and curettage without imaging monitoring, i. e. blindly, demonstrably increases the risk of perforation of the uterine wall, excessive bleeding, and intracavitary residues. Studies show that the use of IOUS can reduce the risk of complications and lead to faster and safer operations. Particularly for hydatidiform moles, IOUS is ideal for assessing a myometrial invasion [14] [15] [16] [17] [18].

Ectopic pregnancies

Ectopic pregnancies can pose significant challenges for surgical treatment, especially if they are not conventional tubal pregnancies. The literature mainly includes reports about IOUS in the surgical treatment of pregnancies in a cesarean scar of the uterus, where complication rates are described at 8–14 %. With regard to safe localization, protection, and preservation of healthy tissue, as well as preventing severe bleeding, IOUS is irreplaceable when using saline curettage/vacuum aspiration or inserting an intrauterine balloon. Its use also leads to shorter procedure times, minimizes the risk of residues, and thus reduces complication rates [19] [20] [21] [22].

Intramural and subserous uterine myomas

Preoperative transvaginal sonography and magnetic resonance imaging (MRI) already provide good diagnostics with regard to the localization and extent of myomas. Especially in intramural myomas, the detection rate can be improved by using IOUS. In this context, a clinical study was able to demonstrate the benefit of IOUS using contact sonography of the uterus during open myomectomy in 64 women. A total of 182 myomas were identified by preoperative transvaginal and abdominal ultrasound examination. Using IOUS, an additional 46 previously undiagnosed myomas with a mean maximum diameter of 11.82 mm (median 11.00 mm; range 5–25 mm) were identified [23]. Another clinical study of 135 patients confirmed these results and showed a double detection rate for laparoscopic IOUS (n = 818), followed by MRI (standardized second reading; n = 619), conventional MRI (n = 562), and transvaginal ultrasound (n = 403) [24]. Basically, imaging is clearly superior to palpation, because it avoids open surgical interventions, and IOUS, in particular, improves the precision of myoma removals [25] [26] [27].

Endometriosis and adenomyosis uteri

Adequate preoperative imaging diagnostics of endometriosis in the pelvic, rectal, and sigmoid regions is often a major challenge. In cases of deep infiltrating endometriosis, the additional use of IOUS can provide a benefit for reliable targeting and fine-tuning of the resection volume [28] [29] [30] [31].

A special form of endometriosis is adenomyosis uteri, for which sonography has a particularly important role in diagnosing. For a long time, the diagnosis of adenomyosis uteri was purely clinical, but the introduction of standardized ultrasound classifications has provided more clarity [5] [32]. Additionally, with regard to interventional ultrasound, we should also mention the scientific approach of a study, in which a laparoscopic, sonographically guided punch biopsy of the uterus was performed to provide histological confirmation of uterine adenomyosis.

Urogynecology

Sonographic examination of the pelvic floor allows assessment of the urethra and bladder neck, rectum and anorectal junction, integrity of the levator ani muscles, and visualization of reconstructive vaginal mesh implants and tension-free slings (TVT) to treat stress incontinence [33]. This ensures that they can be protected during surgical interventions and helps to optimize pelvic floor reconstructions [34]. In this context, a study has shown that IOUS enables improved placement of a TVT-O (tension-free vaginal tape obturator) [35]. Another study describes the use of intraoperative Doppler sonography with a full bladder used to visualize the ureteral jet in order to demonstrate its function [36].

IOUS in gynecologic oncology

Borderline ovarian tumor

IOUS is used to determine the resection volume in borderline ovarian tumors. By precisely demarcating the tumors from the healthy remaining ovaries, surgery can be performed in an especially tissue-sparing manner in order to preserve fertility [37] [38] [39].

Myometrial invasion in endometrial carcinoma

Another application area for IOUS is its use to assess myometrial invasion in endometrial carcinoma. Intraoperative ex-vivo high-resolution sonography (IEVHS) in 45 patients correctly estimated the myometrial invasion depth in 39 of 45 cases (86.6 %), whereas frozen section examination correctly assessed the myometrial invasion depth in 41 of 46 cases (91.1 %) [40]. Because the depth of myometrial invasion is a decisive factor for the indication for lymph node dissection, it is important to make the most accurate assessment possible preoperatively, or at the latest intraoperatively, in order to optimize treatment planning and to avoid a second procedure. IOUS used directly on the uterine wall can improve the predictive value of pre-op imaging.

Brachytherapy for cervical cancer

IOUS supports the precise placement of applicators for intracavitary brachytherapy in the treatment of cervical cancer. IOUS has been shown to reduce the incidence of uterine perforation. Ultrasound guided positioning of applicators improves local tumor control and ensures the best possible treatment results [41] [42] [43].

Liver metastases

IOUS has long played an important role in identifying liver metastases, particularly in cancers where conventional imaging techniques, such as computed tomography (CT) or preoperative sonography, cannot adequately detect metastases. Although most studies in this area have been conducted in the context of colorectal cancer, there is evidence that IOUS may also be helpful in gynecological cancers. In liver surgery, IOUS, supported by contrast agents and 3 D animation, is seeing its most advanced use to date [44] [45]. In the current issue of the European Journal of Ultrasound, Bitterer et al. have published an excellent article on the use of contrast-enhanced IOUS in liver metastases.

Visualization of nerves and lymph nodes in the retroperitoneum

While the applications listed above are already in clinical use, the following scientific research areas are worth highlighting. For example, an ongoing study is investigating the intraoperative sonographic imaging of pelvic nerves during urogynecologic surgery ([Fig. 2]). Another study deals with the intraoperative sonographic assessment of the pelvic sentinel lymph node in cervical and endometrial carcinoma during laparoscopic and robotic gynecologic oncology procedures ([Fig. 3]).

Fig. 2 Laparoscopically guided sonography for visualization of the genitofemoral nerve before opening the retroperitoneum. A – Laparoscopic placement of the drop-in transducer in the area of the right psoas muscle to expose the right genitofemoral nerve; B – Sonographic image of a splitting right genitofemoral nerve; both branches are outlined in green in the figure; C – Anatomical correlation of the sonographic image after opening the right pelvic wall; a green bar marks the sonographic plane in the figure.

Fig. 3 Laparoscopically-assisted IOUS of the sentinel lymph node in a patient with cervical cancer. A – Positioning of the drop-in transducer in the area of the ICG (indocyanine green) positive sentinel lymph node in the area of the right external iliac artery; B – Sonographic image of the sentinel lymph node before preparation, with oval configuration and preserved cortex structure; outlined in green in the figure; C – The sentinel lymph node is prepared with a gamma probe intraoperatively to measure the technetium activity of the marked sentinel lymph node; outlined in green in the figure.

Benefits and challenges of IOUS

IOUS provides precise, real-time visualization during surgery, thereby improving surgical targeting and reducing the risk of complications. IOUS is especially beneficial in minimally invasive and, in particular, robotically-assisted procedures, where better visual information can potentially compensate for a lack of tactile feedback. The standardized reporting and documentation also enable improved anatomical mapping. In particular, IOUS also offers improved documentation options compared to conventional surgical procedures, which not only has a positive effect on the quality assurance and transparency of surgical interventions but is also ideally suited to demonstrably prevent errors in treatment.

Nevertheless, IOUS depends on the expertise of the user, as specialized knowledge is needed to generate and interpret ultrasound images. As a result, it is important to further standardize reporting and provide comprehensive training for IOUS users.

Conclusion

IOUS has established itself as a valuable tool in gynecological surgery. It improves surgical precision and reduces complications, particularly in complex and minimally invasive procedures. Despite some challenges, such as dependence on surgeon expertise, IOUS provides significant benefits and has the potential to further transform the future of gynecological surgery. Ongoing research and the integration of new technologies will further expand the application scope for IOUS in gynecological surgery.

Dr. Sascha Hoffmann

Prof. Markus Hoopmann

• References

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Publikationsverlauf

Artikel online veröffentlicht:
11. Dezember 2024